Posted by sam on February 02, 2001 at 17:29:41:
I'm trying to determine the pressure angle of 12 tooth pinion gear, 3.5 inches outside diameter. This gear is from the final drive unit from and 1960 vintage International Harvester tractor. Tooth depth is about 9/16 inch. There is no top land - the teeth are sharp. A standard full depth 4DP #8 20 degree milling cutter will form a somewhat wider bottom land than this gear has. The mating gear has 59 teeth, 14 inches outside diameter, which is smaller than a typical 4DP.
The service manual lists the tooth thicknesses at the pitch circle as 0.470 inches and 0.253 inches for the pinion and gear respectively, which is the only published data that I can find. Rough measurements using these tooth thicknesses indicate pitch diameters of 2.75 and 13.75 inches. This is confusing as the normal pitch diameters would be 3 inches and 14.75 inches respectively.
Any ideas on how to determine the pressure angle?
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